Patients with deep vein thrombosis of the lower extremities andor pelvis are eligible for this protocol if their thrombosis has been symptomatic for no more than 14 days and if their bleeding risk is very low. They are hospitalized for 3-7 days for up to 4 daily injections of rtPA directly into their thrombi. Simultaneously they receive anticoagulation, which is continued for 6 months. We have completed the treatment phase of the protocol after accrual of the 30th patient. Extensive thrombolysis had been achieved with low doses of alteplase in every patient, and there have been no serious adverse events. As the protocol is approved for 30 patients , we have completed accrural of patients for the protocol. Although no new patients can be recruited, the protocol now enters follow up phase that last 5 years for each patient. During this follow up period we are permitted to treat the first recurrence of DVT in a previously treated protocol patient if the patient returns to us when 14 days of onset of symptoms. this allows us to get precise evaluation of extent of DVT if a recurrence occurs. Two years ago , we reported successful treatment of a recurrence in a 21yo WM , who 2year after initial treatment developed recurrent extensive DVT during convalescence after ORIF for a fibula fracture. This past year, one previously treated protocol patient notified us of a recurrent DVT in the previously treated leg, after having stopped anticoagulation for a few months. Since this recurrence occurred at 5years +1 month , or 1 month beyond stipulated follow up period in the protocol, this patient required and received a special exemption for retreatment which again successfully and safely restored blood flow and patency of his deep veins. While the thrombolytic treatment appears to be safe and therapeutic, it does not appear to obviate the need for long term anticoagulation in patients who present with idiopathic DVT.